Interactive Effects of Task Load and Music Tempo on Psychological, Psychophysiological and Behavioural Outcomes During Simulated Driving

Abstract
Data were checked for univariate outliers using standardised scores (z > ± 3.29) and for multivariate outliers using the Mahalanobis distance test (p
< .001; Tabachnick & Fidell, 2019). Data were also examined for
the parametric assumptions that underlie within-subjects ANOVA
(Tabachnick & Fidell, 2019), other than the behavioural data from
video analysis, which were derived from frequency counts. Where the
assumption of sphericity was violated, Greenhouse–Geisser-adjusted F tests were used.
Initial
analyses employed repeated-measures (RM) 2 (Load) × 3 (Tempo) (M)ANOVAs
for the three psychological measures (i.e., RSME, NASA-TLX, and Affect
Grid) and cardiac measures (HR and HRV indices). Additionally,
exploratory analyses were conducted using a mixed-model approach,
adopting the between-subject factors of personality (introvert
vs. extrovert), sex (women vs. men), and age group (young adults vs.
middle-aged adults). Significant F
tests were followed up with pairwise/multiple comparisons, or in the
case of interaction effects, examination of 95% confidence intervals
(95% CIs) to identify where differences lay. Behavioural
data were collated for the urban environment (high load) simulation
under the following categories: (a) video data pertaining to four
triggers (pedestrian, garbage truck, traffic lights, and vehicle
cutting); (b) and simulator-derived data from the accelerator and brake
pedal positions (i.e., 0 = no pressure applied, 1 = maximum braking);
(c) mean speed (mph), and (d) course completion time (min). For the
highway environment (low load), simulator data were collated for: (a)
accelerator and brake pedal positions; (b) mean speed, and (c)
completion time. From among these data, where parametric assumptions
were not met and transformations would not serve to normalise the
distribution, nonparametric analyses was adopted using rank-based,
nonparametric tests. Specifically, the Wald-type
statistic (WTS) and the ANOVA-type statistic (ATS) was computed within
the nparLD package (Noguchi et al., 2012) of data analysis software R. In
the absence of the load factor for the trigger and pedal data, a
within-subjects, one-way ANOVA for the effect of music tempo was
computed. In the exploratory analyses, a factorial approach was used,
with a series of mixed-model ANOVAs 3 ([Tempo] × 2 [Personality], 3
[Tempo] × 2 [Sex], and 3 [Tempo] × 2 [Age Group]). Note that the main
effect of tempo for trigger and pedal data is relevant to the main
analysis but in the interest of parsimony is incorporated within
exploratory factorial analyses.

Detailed Description of Data File

This SPSS data
file contains the demographic data (i.e. sex, age, age group [1 = young adult,
2 = middle-aged adult], personality [1 = introvert, 2 = extrovert]) for each of
the 46 participants (presented with one participant per row). Behavioural measures
relating to the driving simulation are included. These include the elapsed time
(mins) for each trial. Also, mean speed (mph), brake pedal use (i.e. 0 = no pressure applied, 1 =
maximal braking), accelerator pedal use (i.e., 0 = no pressure applied, 1 = maximal acceleration)
and risk ratings (on a scale from 1 [safe driving] to 4 [reckless
driving]). Note that these performance-related measures appear 12 times in
total; that is for each simulator trigger (i.e. a pedestrian who walked at 5 km/h
across a zebra crossing, a garbage truck that moved slowly in the left-hand
lane and prompted an overtaking manoeuvre, traffic lights that changed to red,
a slow vehicle on a stretch of road on which overtaking was prohibited and a
vehicle that cut across unexpectedly at a four-way intersection) across all three
high-load (urban) conditions. Additionally, the scores across all conditions
for the measures of the NASA Task Load Index (NASA-TLX), Affect Grid (affective
valence and affective arousal), Rating Scale Mental Effort (RSME) and wordsearch
task are included. The psychophysiological measures of heart rate variability
(HRV) and mean heart rate (HR) are also included. For HRV and HR, specifically,
we present mean HR, minimum HR, maximum HR, standard deviation of normal RR
intervals (SDNN), HR standard deviation and root mean square of successive
differences (RMSSD). z-scores (i.e. standardised scores) for each
variable are also included. Note that each participant was exposed to six
experimental conditions (high load/fast tempo, high load/slow tempo, high load/no
music, low load/fast music, low load/slow music and low load/no music). Accordingly,
the measures that pertain to each trial (i.e. NASA-TLX, RSME, Affect Grid,
wordsearch task, HRV indices, risk ratings, mean speed, brake pedal use and
accelerator pedal use) appear six times in the data file.